The Quartz Crystal Microbalance (QCM) is a well-established technology for quantifying small changes in mass. The long-term objective of this program is to improve the QCM so that it is suitable for use as a field test for the common, foodborne bacteria. To do this, we will modify the standard quartz crystal (QC) used in the QCM so as to increase its background rejection capabilities. This will involve innovations to the design of the QC used as the detector to the electronics. We will utilize standard technology to deposit a uniform coating of antibody directed against E. coli onto the surface of the QC. We will use utilize commercially available preparations of E. coli and Pseudomonas to demonstrate that the innovations introduced to the QC design and the electronics of the QCM allow a single QC to serve as both the experimental and the reference detectors. Thus, the modified QCM can discriminate between specific and non-specific binding of mass to the QC. We will use a second antibody, labeled with horseradish peroxidase to generate an insoluble reaction product to further amplify the mass of bacteria attached to the QC. Furthermore, we will utilize glutaraldehyde to non-selectively bind bovine serum albumin to antibody on the surface of both the conventional and modified QCs. Only the modified QC will be able to discriminate between specific binding of E. coli to the antibody and the non-specific cross-linking of BSA to antibody. We believe that our innovations will be of particular value in field tests in which there will be relatively small amounts of pathogenic agent and relatively large amounts of nonhazardous materials. In Phase II of the project, we will apply the technology developed in Phase I to the detection of other common foodborne bacterial contaminants. We will also extend our working relationship with academic laboratories to further test the device. We will work with diagnostics companies to determine their willingness to commercialize this technology.